Palladium Complexes Research Articles

Synthesis and Reactivity of Palladium Complexes Bearing Phosphino-Amidinate Ligands: O–H Bond Activation by Metal–Ligand Cooperation

Synthesis and Reactivity of Palladium Complexes Bearing Phosphino-Amidinate Ligands: O–H Bond Activation by Metal–Ligand Cooperation

A Comprehensive Evaluation of a Coumarin Derivative and Its Corresponding Palladium Complex as Potential Therapeutic Agents in the Treatment of Gynecological Cancers: Synthesis, Characterization, and Cytotoxicity

Background: The aim of this research is the synthesis and characterization of coumarin-palladium complex and the investigation of the cytotoxicity of both the ligand and the complex. Methods: The palladium( II) complex (CC) was obtained in the reaction between (E)-3-(1-((4-hydroxy-3-methoxyphenyl)amino)ethylidene)-2,4-dioxochroman-7-yl-acetate (CL) and potassium-tetrachloropalladate(II) and characterized using IR and NMR spectra, experimentally and theoretically. Cytotoxicity of CL and CC were determined for human cervical carcinoma HeLa, ovarian cancer A2780, hormone dependent breast cancer MCF7, and colorectal cancer HCT116 lines. The interaction of investigated compounds with HSA was followed by spectrofluorimetric method. The binding mechanism in the active pocket was assessed via molecular docking simulations. Results: A low mean absolute error between experimental and theoretical data proved that the optimized structure corresponded to the experimental one. Both compounds showed a satisfactory selectivity index towards neoplastic cells. The binding affinity of tested compounds to the HSA were confirmed. The molecular docking showed a much lower change in the Gibbs free energy of binding for CC compared to CL. Conclusions: The obtained results revealed that CL and CC exhibit significant effects on several cancer cell lines and good binding properties to HSA, while molecular docking discovered that CC has the most pronounced activity against alpha-fetoprotein.

Innovative electrochemical sensor based on platinum group metal complexes for determination of nitrite: Application for simultaneous detection of nitrite and tartrazine

In the context of this experimental study, new palladium and ruthenium complexes based on a symmetric ligand, named 2E-Peaemp ((3E,3’E)-3,3’-(((piperazine-1,4-diyl bis (ethane-2,1-diyl)) bis (azanediyl)) bis (ethan1-yl-1-ylidene)) bis (6-methyl-2H-pyran-2,4(3 H)-dione), and their hybrid compounds with carbon nanotubes were prepared and characterized. The sensors prepared using a cavity microelectrode (MEC) modified with a mixture of graphite (CG), carbon nanotubes (MWCNT) and the synthesized complexes (Pd-2E-Peaemp and Ru-2E-Peaemp) were applied to detect the pollutants such as Nitrites and Tartrazine separately and simultaneously in aqueous solutions and real samples (Tap water, wastewater and bottled commercial spring water). The detection limits (LODs) determined for nitrites and tartrazine are obtained using MEC/CG-MWCNT-Pd-2E-Peaemp electrode, and the electrochemical measurements demonstrated a sensitive and rapid response in the analysis of these species. LODs are 0.39 µM and 0.11 µM, respectively, within the concentration range of 0–909 µM for nitrites and 0–97 µM for tartrazine. This electrode modified by the palladium complex is also used to simultaneously detect nitrite and tartrazine analytes using the differential pulse voltammetry (DPV) technique, indicating that the proposed sensor can be an interesting alternative tool to measure these species in real samples. The application of this electrode in these natural environments reveals that the developed sensor can detect low concentrations of nitrite (NO2-; trace) without any interference from other ions substances as acetate (CH3COO-), borate (BO3−3), phosphate (PO4−3), dihydrogen ( 2 H+), sulfate (SO4−2), sodium (Na+), hydroxide (OH-), potasium (K+), chloride (Cl-), magnesium (I) ( Mg+), nitrate (NO3-), calcium (Ca2+), carbonate (CO3−2).

Enhancing stability of cationic palladium complexes with hemilabile 2-benzyl oxazoline ligands: Structural insights and catalytic implications

This article describes the synthesis and characterization of Pd cationic complexes incorporating mono(2-benzyl oxazoline) ligands. Our study focuses on exploring the impact of electrostatic interactions of aromatic π-electrons of the benzyl group, aimed at enhancing the structural rigidity of cationic Pd complexes. Introduction of an aromatic moiety, which weakly coordinates with the Pd cation, led to a two-fold increase in the stability of the Pd cationic complex compared to complexes lacking any coordinating substituents. This research represents the initial instance of a cationic Pd complex with 2-benzyl oxazolines, highlighting the importance of weak electrostatic interactions in elucidating the three-dimensional structure of a metal complex.

First report on the investigation of the pH dependent behavior in the complexes of palladium(II) acetylacetonate with isomers of dinitrobenzoate: Combined single crystal X-ray diffraction and Hirshfeld surface calculations

The novel six palladium acetylacetonate [Pd(acac)2] and isomers of dinitrobenzoate anions (e.g., 3,5-dinitrobenzoate (L1) and 2,4-dinitrobenzoate (L2)) based complexes (1-6) have been synthesized via a facile hydrothermal route. These complexes are further characterized by single crystal X-ray diffraction (SCXRD), IR spectroscopy, NMR spectroscopy, powder X-ray diffraction (PXRD), UV-vis spectroscopy, and thermogravimetric analysis (TGA). For the synthesis of these complexes, the initial precursors of isomers of dinitrobenzoates, i.e., 3,5 dinitrobenzoic acid (L1H) and 2,4 dinitrobenzoic acid (L2H) have been used at different pH conditions. The study evaluates the ability of the acetylacetonate group to act as a hydrogen bond acceptor in the presence of isomeric dinitrobenzoate ligands. The basic structure of Pd(acac)2 undergoes changes due to the varying chemical environment at different pH conditions. At lower pH levels, protonation of the acac group has occurred (e.g., complex 1), leading to changes in the coordination environment around the Pd(II) center. At the slightly basic pH value (⁓10), one of the acac anion is replaced with two ammonia molecules (e.g., complex 2, 4, and 5). Further increasing pH to 14, results in the replacement of both acac anions with four ammonia molecules (e.g., complex 3 and 6). The complexes 4 and 5 are pseudopolymorphs or solvates that are recovered from the same reaction mixture showing different morphology. These results are confirmed by NMR spectroscopy and single crystal X-ray diffraction. The crystallographic results have been amply supplemented by Hirshfeld surface analysis and other spectroscopic studies. The structural changes in complexes can impact the electronic properties and behavior of Pd(acac)2 in different chemical reactions. Therefore, it is important to consider the pH conditions when studying the structure and reactivity of Pd(acac)2 in various applications.

Study on photodissociation spectra and decay pathways of gas-phase PdCl3– and PdCl2– anions by electrospray ionization mass spectrometry and MRCI calculation

We investigate photodissociation of the gas-phase palladium complex anions, Pd(II)Cl3- and Pd(I)Cl2-, both experimentally and theoretically. Visible photodissociation mass spectrometry reveals that the main dissociation channels differ for Pd(II)Cl3- and Pd(I)Cl2-; the former yields neutral chlorine atom (Pd(I)Cl2- + Cl) whereas the latter affords chloride anion (Pd(I)Cl + Cl-). Absorption spectrum and photodissociation channels are predicted using the MRCI method. The observed absorption spectrum and dissociation product for Pd(II)Cl3- agree with the MRCI calculation, whereas those for Pd(I)Cl2- do not, which suggests that some relaxation process such as internal conversion significantly contributes to the photodissociation of Pd(I)Cl2-.

Palladium-Catalyzed Acetoxylation of γ-Dehydro-aryl-himachalene: The Synthesis of a Novel Allylic Acetoxylated Sesquiterpene and a π-Allyl Palladium(II) Complex.

Allylic oxygenated derivatives of himachalenes are highly valued molecules due to their potential applications in perfumery, cosmetics, and pharmaceuticals. Previous attempts at catalyzed allylic oxidation of himachalenes led to the formation of a very stable η3-allyl palladium complex, preventing any further reaction development. Herein, we present the first successful palladium-catalyzed synthesis of a novel allylic acetoxylated derivative of himachalenes. This reaction was achieved by incorporating an aromatic ring into the substrate structure. The resulting intermediate complex was isolated and characterized using nuclear magnetic resonance spectroscopy and X-ray crystallography. Density functional theory (DFT) calculations were performed to compare the reactivity of the newly synthesized complex with previously reported ones. The theoretical results confirm that the introduction of an aromatic ring enhances the reactivity of the η³-allyl palladium complex, thereby facilitating the desired transformation.

Revisiting Isomerism in Square Planar Palladium NHC Complexes with NacAc Chelators.

Quantifying the donor ability of bidentate ligands in inorganic chemistry is not straightforward, and the Huynh electronic parameter for chelators (HEP2) presents a rare solution to the task. Aiming to extend the ligand scope in this work, the soundness and practicality of HEP2 was further scrutinized with seven stereoelectronically diverse β-ketiminato ("NacAc") chelators using palladium complexes of the type [PdBr(iPr2-bimy)(ArNacAc)] (iPr2-bimy = 1,3-diisopropylbenzimidazolin-2-ylidene). Notably, the unsymmetrical nature of this κ2-N,O ligand family allowed for an intriguing exploration into isomerism in the square planar PdII products, which depends on the N-aryl ortho- and para-substituents based on experimental and theoretical findings. The HEP2 values of both isomeric forms correlate well with the widely used σp Hammett constants, which reinforces the reliability of this modern methodology.

Structural Study on Alkali‐Carboxylate Functionalized Late‐Transition Metal Bis(dithiocarbamate) Complexes

AbstractLithium, sodium, and potassium derivatives of amino‐acid derived bis(dithiocarbamate) complexes of bivalent nickel, palladium, platinum, and copper are readily available by treatment of the carboxylic‐acid functionalized complexes with the respective alkali metal hydroxide. Representative derivatives of the types A4[M(L1)2], A2[M(HL1)2], A[M(HL1)(H2L1)] (N‐dithioato‐iminodiacetate, L1), and A2[M(L2,3)2] (N‐dithioato‐l‐prolinate, L2, and ‐N‐benzylglycinate, L3; A=Li, Na, K; M=Ni, Pd, Pt, Cu) were isolated and characterized by spectroscopic and thermal methods. Six entries were accessible to single‐crystal X‐ray structure determination, revealing the presence of different coordination‐polymeric structures and hydrogen‐bonded assemblies comprising solvent‐separated cations in the solid state. While the transition metal always retains its all‐sulfur coordination with defined geometry, the alkali metals are structurally more flexible. The latter are usually coordinated by carboxylate and water, but additional interactions with sulfur donors are also relevant in some cases.

Palladium(II) and platinum(II) thiophene-based thiosemicarbazones: Synthesis, properties, and anticancer studies

The aim of this study was to synthesize and investigate the cytotoxic profile of four palladium(II) and two platinum(II) complexes containing thiosemicarbazones derived from thiophene against tumor cells. They were fully characterized by various analytical techniques, including 1H, 13C{1H}, 31P{1H}, 135DEPT NMR, IR, UV–vis, X-ray diffraction, molar conductivity, and theoretical. Several techniques were used to evaluate the interaction of the complexes with DNA, such as gel electrophoresis, UV–vis spectroscopy, circular dichroism, viscosity measurements, fluorescence assay with Hoescht 33,258, and molecular docking. The results indicated that the complexes exhibited electrostatic and/or groove interaction with DNA, but only at high concentrations (100 µM). In vitro, cytotoxicity assays were performed using the MTT method, and the palladium(II) complexes showed remarkable cytotoxic activity against A549 and A2780cis cell lines. In particular, the PdT compound showed cytostatic behavior against the A549 tumor line, while the PdCH3 compound showed cytotoxic behavior against the A2780cis line. Further investigation of the most promising compound, PdCH3, in A2780cis revealed that it induced apoptosis by promoting cell accumulation in the sub-G1 phase and causing partial mitochondrial membrane depolarization. In addition, this complex significantly inhibited colony formation, leading to significant changes in cell morphology. However, no inhibition of cell migration was observed in the 3D cell model of DAOY cells. These findings provide valuable insights and structural features for the design of selective palladium complexes targeting ovarian tumor cells (A2780cis). The study highlights the potential of these complexes as cytotoxic agents against specific cancer cell lines, paving the way for future advances in medicinal chemistry research.

Effect of N-substituted aliphatic glycine presence on bioactivity, cytotoxicity, and selectivity of Pt(II) and Pd(II) complexes in cancer treatment

In this study, four new platinum (II) and palladium(II) complexes were synthesized to develop metallo-drugs that can attach to DNA and prevent the division of cancer cells. The complexes, 1: [Pt(bipy)(LP)]NO3, 2: [Pt(bipy)(LA)]NO3, 3: [Pd(bipy)(LP)]NO3, and 4: [Pd(phen)(LP)]NO3 (where LP is propylglycine, LA is 2-heptyl glycine, bipy is 2,2-bipyridine, and phen is 1,10-phenanthroline), were structurally characterized using computational and experimental analysis. Their stability, solubility, and lipophilicity were evaluated. Single-crystal X-ray and powder X-ray crystallographic analyses were performed for [Pt(bipy)(LA)]NO3. Density functional theory calculations were performed to investigate the reactivity, stability descriptors, and natural bond orbital analysis of these complexes. The in vitro cytotoxicity of these substances was examined against the human colorectal carcinoma (HCT116), A549 (Human Caucasian lung carcinoma), MCF7 (breast cancer), and HFF (Human Freskin Fibroblast) cell lines. According to the findings, complexes 4 and 3 had near oxaliplatin concentrations and more than carboplatin due to lipophilic ligands in their structure. Also, regarding IC50 values on normal HFF cell line, 4 is selectively toxic against the A549 cancer cell line with SI=5.6. Fluorescence, electronic absorption spectroscopy, and CD spectroscopy were used to investigate the binding affinities of compounds to CT-DNA and HSA. The results revealed that they could interact with CT-DNA through groove mode and with HSA via hydrogen bond and van der Waals forces. Electronic absorption and CD spectra indicated that compounds changed the way the HSA folded by increasing the proportion of a-helix. The binding posture of the metal complex to both biomolecules was predicted using docking simulation, which also verified the groove binding for DNA-complex. The findings indicated that complex 4 had a greater negative docking energy and a higher propensity for CT-DNA and HSA interaction.

Structural, DNA/BSA binding interactions and cytotoxicity studies of carboxamide (pyridyl)pyrazine palladium(II) complexes

Structural, DNA/BSA binding interactions and cytotoxicity studies of carboxamide (pyridyl)pyrazine palladium(II) complexes

Palladium(II) complexes comprising thiazole-hydrazone Schiff base ligand: Synthesis, structure and catalytic activity in Suzuki-Miyaura coupling reactions

The reaction of PdCl2 and Pd(OAc)2 with (E)-2-(2-(pyridin-2-ylmethylene)hydrazinyl)benzo[d]thiazole (HL) in methanol resulted in the formation of two neutral mononuclear Pd(II) complexes. By using PdCl2 two kinds of crystals with general formula of [Pd(Cl)L]·0.5(C2H5OH) (1a) and [Pd(Cl)L] (1b) were obtained while Pd(OAc)2 gave one type of crystal with general formula of [Pd(OAc)L]·0.5(H2O) (2). These complexes were characterized using spectroscopic methods, and their molecular structures were determined by single crystal X-ray diffraction analysis. In these complexes, the ligand coordinates to the Pd(II) core through the nitrogen atoms of the thiazole ring, pyridine ring, and imine moiety, acting as tridentate mononegative NNN donor ligand. These palladium(II) complexes were also found to exhibit catalytic activity in Suzuki-Miyaura coupling reactions.

NNN type pincer Pd (II) complexes of pyridine-2,6-dicarboxamides: Catalytic activity and supramolecular formation

Pyridine-2,6-dicarboxamide, NNN pincer type pro-ligands, and their palladium complexes were synthesized. The prepared pro-ligands and complexes were characterized with several characterization techniques (FT-IR, 1H NMR, 13C NMR, and UV-vis analyses). The molecular structure of the acetonitrile-N2,N6-bis(2-bromophenyl)pyridine-2,6-dicarboxamidopalladium(II) complex has been determined by single crystal XRD measurement. This complex contains intramolecular and intermolecular H-bonds, C–H⋅⋅⋅π and face-to-face π⋅⋅⋅π interactions. In addition, two synthons were found in the crystal lattice that have been generated through hydrogen-bond interactions. Homo-synthons (R22(12)), which forms through C–H⋅⋅⋅O intermolecular interactions (2.816 Å for C15–H15⋅⋅⋅O1 and 2.603 Å for C13–H13⋅⋅⋅O2) and hetero-synthons (R21(8)), that generated via C–H⋅⋅⋅N intermolecular interactions (C21–H21C⋅⋅⋅N4, 3.439 Å). Furhermore, homo-synthons (R33(11) and R22(9)) through intermolecular contacts were determined between the palladium complex and the acetonitrile molecules. Furthermore, a quantitative analysis of the noncovalent interactions within the structure was performed using Hirshfeld surface and two-dimensional fingerprint plot analyses. The three-dimensional arrangement of the crystal packing was assessed during the energy-framework calculations, revealing that the electrostatic energy framework had a considerable influence on the dispersion energy framework. The [PdL5] complex provided a conversion of more than 98% and a yield of more than 98% in the shortest time among other catalysts, in which the Suzuki-Miyaura C-C cross-coupling reaction (SMR) was carried out with the 4-bromotoluene substrate. The activity of [PdL5] complex was then examined in the reactions of two other substrates, 1-bromo-4-isobutylbenzene and 2-bromo-6-methoxynaphthalene. Although a yield of over 97% and a conversion of over 97% were observed in the reaction of 1-bromo-4-isobutylbenzene after two hours, the reaction of 2-bromo-6-methoxynaphthalene achieved complete conversion and a yield of over 99% within just one hour.

Two bis-maltol-polyamines: Synthesis, characterization and studies of their palladium(II) complexes exploring their potential anticancer activity

The interest in the antineoplastic and binding properties shown by the bis-maltol polyamine family, particularly Malten and Maltonis, prompted us to study the Pd2+ complexes of these latter from both a biological and metallo-receptor point of view. The Malten-Pd2+ complex can lodge hard species such as Sr2+ in its coordination-driven preorganized pocket, as confirmed by X-ray diffraction. UV–Vis and NMR data showed that Malten-Pd2+ forms even at acidic pH and exists in aqueous solution in a wide range of pH. The mononuclear complex is stable enough not to release Pd2+ in solution for a long period of time (at least one week), thus Malten-Pd2+, similarly to Maltonis-Pd2+, is suitable to be tested in biological analyses. Studies on the U937 cell line revealed that the effect on cell survival reduction induced by Malten is partially lost in Malten-Pd2+, while no differences where monitored between the effects of Maltonis-Pd2+ and Maltonis, suggesting that the availability of free maltol moieties, that is retained in Maltonis-Pd2+, but not in Malten-Pd2+, is crucial to guarantee the biological activity of these compounds.

Construction and Characterization of Magnetic Fe3O4 Nanoparticles Supported Palladium Complex: Research on Synthesis of Aryl Nitriles and Tetrazoles

Construction and Characterization of Magnetic Fe3O4 Nanoparticles Supported Palladium Complex: Research on Synthesis of Aryl Nitriles and Tetrazoles

N-Heterocyclic Carbene-Derived Carbon Disulfide Radical Ligands for Palladium Diradicals.

N-heterocyclic carbenes (NHCs) are recognized for their ability to stabilize various main group radicals; however, NHC-derived, sulfur-based radicals remain rare. In this study, we successfully synthesized and characterized a series of palladium diradical complexes that featured new sulfur-based radical ligands from NHC-carbon disulfide adducts. Spectroscopic and computational characterizations of the palladium complexes confirmed the open-shell singlet ground state, which resulted from the antiferromagnetic coupling of two unpaired electrons on each ligand. Proton nuclear magnetic resonance relaxometry was used to experimentally confirm the presence of these unpaired electrons. Moreover, the redox behavior of the complexes was localized on the ligand center, confirming the redox activity of the ligands. The discovery of this sulfur-based, redox-active radical ligand underscores the versatility and significance of NHC-derived radicals, thereby expanding the repertoire of radical ligands and opening new avenues for advanced material and catalytic systems.

Synthesis, Structural Characterization and Catalytic Application of Ferrocenyl Based Bis(pyrazolyl) Palladium Complexes.

Here we report, synthesis of ferrocenyl based bis(pyrazolyl) palladium complexes. The catalytic utility of the complexes in the cross-coupling of triarylbismuthanes and aryl bromides was evaluated. Our ferrocenyl based palladium complex showed wide substrate scope for both triarylbismuthanes and aryl bromides. Further, the current catalytic system also showed superior activity over the well-established palladium-phosphine catalytic system using triarylbismuthanes as reagents.

Synthesis and Characterization of Air‐Stable Palladium(II) and Copper(I) Ph‐Garphos Complexes and their Applications to Asymmetric Catalysis

AbstractAir‐stable palladium(II) and copper(I) complexes containing the 4,4′,6,6′‐tetramethoxybiphenyl‐2,2′‐diyl)bis(diphenylphosphine) ligands, (R)‐Ph‐Garphos ((R)‐L1) and ((S)‐Ph‐Garphos ((S)‐L1), were synthesized and characterized by 1H‐, 13C‐, and 31P{1H} NMR spectroscopy and elemental analyses. The PdCl2((R)‐Ph‐Garphos) ((R)‐1) and PdCl2((S)‐Ph‐Garphos) ((S)‐1) complexes were assessed for the Suzuki‐Miyaura cross‐coupling of aryl halides with phenylboronic acid under ambient conditions, or naphthyl substrates under reflux. X‐ray crystal structures of the copper complexes revealed that [Cu((R)‐Ph‐Garphos)I] ((R)‐2) crystallized as a three‐coordinate monomer in the orthorhombic space group P212121 whereas [Cu((S)‐Ph‐Garphos)I] ((S)‐2) crystallized as a tetrahedral (μ‐I) dimer in the same crystal system. The synthesis of the analogous [Cu((R)‐Ph‐Garphos)OAc] ((R)‐3) is also described. Complexes (R)‐2 and (R)‐3 were evaluated for the asymmetric hydrosilylation of ketones wherein enantioselectivities of up to 83 % ee were achieved.

Design, synthesis, and evaluation of some metal ion complexes of mannich base derived from 2-Mercaptobenzimidazole as potential antimicrobial agents

This study aims to prepare new compounds and investigate them spectroscopically and biologically against selected types of positive and negative bacteria and fungi to demonstrate their biological effectiveness. The prepared ligand combining formaldehyde, indole, sulfa benzamide, and 2-mercapto benzimidazole, a Mannich base ligand (L) was synthesized. The six metal ions including Cobalt (II), Nickel (II), Copper (II), Palladium (II), Platinum (IV), and gold (III) have interacted with the ligand and formed new complexes. Different spectroscopic methods, including C.H.N.S., FTIR, UV- Range visible, 1HNMR, 13CNMR, mass spectra, magnetic moment, and molar conductivity were used to suggest the new geometry of the complexes. The result from the infrared spectrum showed that the ligand behaves as tridentate with all prepared complexes. Conductivity analysis revealed the electrolytic nature of palladium, platinum, and gold ions complexes and non-electrolytes. The antibacterial activity of the compounds that were produced was tested using an agar-well diffusion procedure towards two strains of gram-positive as well as two strains of gram-negative bacteria and fungi (Staphylococcus, Streptococcus, Escherichia coli, Pseudomonas aeruginosa, and Candida albicans) respectively at 0.02M. The standard (∆Eo) and (∆Hfo) of ligand and six complexes were calculated using the program Hyper chem 8.0.7. The research established that complexes are more stable than ligands. Calculated HOMO and LUMO and vibration frequencies using (parametric method 3 (PM3)) to find out the active sites in the ligand showed that they can coordinate and note the extent to which the results of theoretical vibrational frequencies are close to the process when calculating the vibrational frequency of the active aggregates.